1. Field of the Invention
The present invention relates to an optical information medium such as a read-only optical disk, an optical recording disk or a magneto-optical recording disk, and more specifically to an optical information medium in which the recording and/or reproducing beam incident side surface displays excellent anti-staining properties and lubricity, as well as superior scratch resistance and abrasion resistance.
2. Disclosure of the Related Art
On the surfaces of optical disks such as read-only optical disks, optical recording disks and magneto-optical recording disks, the stains from various stain materials and the adhesion of fingerprints are caused during use. These stains and adhesion fingerprints are undesirable, and accordingly, the surfaces of optical disks may be subjected to a suitable surface treatment to improve the anti-staining property, reduce the adhesion of fingerprints, and improve the ease with which fingerprints can be removed. For example, a variety of different water repellent and oil repellent treatments are being investigated for the surfaces of optical disks.
Furthermore, the formation of a transparent, scratch resistant hard coat on the recording and/or reproducing beam incident side surface of the optical information medium is also standard practice for improving the scratch resistance of the medium surface. Formation of this hard coat is conducted by applying an active energy ray-polymerizable/curable compound containing at least 2 polymerizable functional groups such as (meth)acryloyl groups within each molecule onto the surface of the medium, and then curing the applied film by irradiation with active energy rays such as ultraviolet rays. However, because this type of hard coat only aims to improve the scratch resistance, little can be expected in terms of an anti-staining effect relative to stain materials such as dust, airborne oil mist or fingerprints.
One example of a hard coat with an anti-staining property relative to organic stains is disclosed in Japanese Laid-open Patent Publication No. 10-110118 (1998), which proposes the blending of a non-crosslinking fluorine-based surfactant with a hard coat agent. The non-crosslinking fluorine based surfactant contains no polymerizable double bonds, and undergoes no crosslinking with the base resin of the hard coat agent.
Furthermore, Japanese Laid-open Patent Publication No. 11-293159 (1999) proposes the blending of a combination of a non-crosslinking fluorine-based surfactant and a crosslinking fluorine-based surfactant with a hard coat agent. Examples of the crosslinking fluorine-based surfactant include fluorinated alkyl (meth)acrylates such as perfluorooctylethyl (meth)acrylate, hexafluoropropyl (meth)acrylate and octafluoropentyl (meth)acrylate. These crosslinking fluorine-based surfactants contain polymerizable double bonds, and undergo crosslinking and fixation to the base resin of the hard coat agent.
Japanese Laid-open Patent Publication No. 11-213444 (1999) discloses the application of a fluorine-based polymer to the surface of a conventional optical disk substrate formed from a polycarbonate or the like.
Japanese Laid-open Patent Publication No. 2002-190136 discloses an optical information medium in which metal chalcogenide fine particles of silica or the like are blended into the hard coat, thereby improving the scratch resistance of the hard coat, and in which a film of a silane coupling agent comprising water repellent or oil repellent groups is provided on the hard coat, thereby further improving the anti-staining properties of the optical information medium surface.